The present invention relates to a waterproof construction of a wiring harness provided at a location in a motor vehicle, where water is likely to be splashed.
As shown in FIG. 1, a wiring harness W/H including a main line W/H-1 and a branch line W/H-2 branching off from the main line W/H-1 is provided between a cabin X and an engine portion Y of a motor vehicle and is mounted on a through-hole of a partition wall 1 between the cabin X and the engine portion Y. The main line W/H-1 extends from a space S1 above each of opposite wheel wells 3 to a space S2 above a radiator support 4 located forwards of the tire houses 3, while the branch line W/H-2 is passed through a through-hole formed on an outer wall 5 of an engine room R so as to extend into the engine room R such that the branch line W/H-2 is connected to a branch joint box (not shown), etc. provided in the engine compartment R.
In the engine portion Y outside the cabin X, water is likely to penetrate into, especially, the space S1 above each of the wheel wells 3 and the space S2 above the radiator support 4. Furthermore, since an upper face of each of the wheels wells 3 and the radiator support 4 functions as a water receiving plate, water which has penetrated into the space S1 or S2 is readily collected on the upper face of each of the wheel wells 3 and the radiator support 4. Therefore, water stored on the upper face of each of the wheel wells 3 and the radiator support 4 is apt to penetrate into the wiring harness W/H provided along the upper face of each of the wheel wells 3 and the radiator support 4.
Meanwhile, water is also likely to penetrate into a distal end portion of the wiring harness W/H, which is coupled with a connector.
Once water has been penetrated into the wiring harness W/H, water enters the cabin X through gaps among wires W in the wiring harness W/H, so that a connector coupled with a distal end of the wiring harness W/H in the cabin X is rusted, thereby resulting in improper connection or shortcircuiting at the connector.
In order to prevent penetration of water into the cabin X through the wiring harness W/H provided at the location where water is likely to be splashed, such a measure is taken that a waterproof tape is wound around the wiring harness W/H by double half-wrap and then, the wiring harness is inserted into a protective sheathing formed by a corrugated tube.
However, even if the waterproof tape is wound around the wiring harness W/H by double half-wrap, it is impossible to completely eliminate a possibility that a gap is formed between the tapes. Therefore, in order to solve this problem, the assignee assigned by the present inventors proposed in Japanese Patent Laid-Open Publication No. 5-193424 (1993) a watertight construction of the wiring harness W/H as shown in FIGS. 2A and 2B. Namely, in the wiring harness W/H provided in the space S1 above each of the wheel wells 3 as shown in FIG. 2A, a predetermined height H is formed between a first branch point P1 of the wiring harness W/H from the grommet 2 and a highest point P2 of the wiring harness W/H in the engine portion Y. Thus, water which has penetrated into the wiring harness W/H from the main line W/H-1 or a connector disposed at a distal end of the branch line W/H-2 in the engine compartment R is collected to the lowest first branch point P1 so as not to proceed towards the cabin X. Furthermore, as shown in FIG. 2B, instead of winding a waterproof tape around a bundle of the wires W by double half-wrap, a waterproof sheet 6 made of resin is wound around the bundle of the wires W and then, a tape 7 is roughly wound around the waterproof sheet 6 so as to firmly bundle the wires W.
When the watertight construction referred to above is employed, the resinous waterproof sheet 6 covers the outer periphery of the bundle of the wires W completely and thus, it is possible to positively prevent water from penetrating into the wiring harness W/H from the outer periphery. However, at the branch point P1 of the wiring harness W/H, the resinous waterproof sheet 6 cannot be wound around the bundle of the wires W in close contact with the outer periphery of the bundle of the wires W. Thus, as shown in FIG. 2A, an edge 6a of the resinous waterproof sheet 6 should be positioned at the branch point P1.
Thus, the branch point P1 cannot be waterproofed by covering the branch point P1 with the resinous sheet 6. Meanwhile, in case the branch point P1 is disposed at a lowermost position for storing penetrating water as shown in FIG. 2A, a portion of the wiring harness W/H, which is not covered by the resinous waterproof sheet 6, is likely to be immersed in stored water.
Furthermore, the distal end portion of the wiring harness W/H in the engine room R, which is coupled with a connector, also cannot be completely covered by the resinous waterproof sheet 6. As a result, water which has penetrated into the wiring harness W/H from the distal end portion proceeds through gaps among the wires W of the wiring harness W/H and thus, is collected at the branch point P1.
In order to solve this problem, the height H is defined between the branch point P1 which is not covered by the resinous waterproof sheet 6 and the highest point P2 of the wiring harness W/H shifted from the engine room R towards the cabin X as described above. Therefore, even if water has penetrated into the wiring harness W/H at the branch point P1, water is caused by the height H to flow to the branch point P1 so as not to penetrate into the cabin X. However, during running of the motor vehicle, pressure in the engine portion Y becomes higher than that in the cabin X, so that negative pressure in the cabin X produces force for sucking towards the cabin X water which has penetrated into the wiring harness W/H. As running speed of the motor vehicle becomes higher, negative pressure in the cabin X rises and thus, the suction force towards the cabin X is increased.
In addition, in case the resinous waterproof sheet 6 is wound around the bundle of the wires W and then, the tape 7 is wound around the resinous waterproof sheet 6 as shown in FIG. 2B, a gap C1 is formed among neighboring ones of the wires W, a gap C2 is formed between the resinous waterproof sheet 6 and outer peripheral ones of the wires W and a gap C3 is formed between the overlapped resinous waterproof sheet 6. Water which has penetrated into the wiring harness W/H up to the branch point P1 is sucked up by capillarity through the gaps C1, C2 and C3 acting as capillary channels.
By the above mentioned sucking of water based on capillarity and the above described sucking of water based on negative pressure in the cabin X, water penetrates into the cabin X through the wiring harness W/H even if the height H is formed on the wiring harness W/H.